The reappearance of a northeast Pacific marine heatwave (MHW) sounded alarms in late summer 2019 for a warming event on par with the 2013–2016 MHW known as The Blob. Despite these two events having similar magnitudes in surface warming, differences in seasonality and salinity distinguish their evolutions. We compare and contrast the ocean’s role in the evolution and persistence of the 2013–2016 and 2019–2020 MHWs using mapped temperature and salinity data from Argo floats. An unusual near-surface freshwater anomaly in the Gulf of Alaska during 2019 increased the stability of the water column, preventing the MHW from penetrating as deeply as the 2013–2016 event. This freshwater anomaly likely contributed to the intensification of the MHW by increasing the near-surface buoyancy. The gradual buildup of subsurface heat content throughout 2020 in the region suggests the potential for persistent ecological impacts.

Here we discuss a global ocean surface mixed layer statistical monthly climatology (GOSML) of depth, temperature, and salinity that includes means; variances; 5th, 50th, and 95th percentiles; as well as skewness and kurtosis. Ocean surface mixed layer properties are influenced by a wide variety of factors that operate over a wide variety of time scales and gravity. Mixed layer depths can shoal very quickly as a result of surface heating, precipitation, or “slumping” of horizontal density gradients. However, deepening the mixed layer in the presence of a strong pycnocline requires substantial buoyancy loss or strong wind mixing, which often takes more time. This pattern is clear in the annual cycle monthly mixed layer depth values, with deepening in the fall much slower than shoaling in the spring. The 95th percentile values are chosen as a reasonable indicator of ventilation depth, robust to extreme outliers. Mean mixed layer depths are on average 0.56 of 95th percentile mixed layer depths, with only 1% of values below 0.31 and 1% above 0.81. Over 71% of mixed layer depth distributions are skewed positive, usually when there are more shallow mixed layer depths than not and deep mixed layers tails are strong. Comparing 95th percentile depth conditions to mean values shows in late winter temperatures are generally lower in the subtropics and salinities generally higher in the subpolar regions, consistent with the importance of temperature in the midlatitudes and salinity in the higher latitudes in setting stratification.

Serendipitous measurements of deep internal wave signatures are evident in variations in the descent rates of certain Deep Argo floats (Deep SOLO models), which oscillate around a slow decrease with increasing pressure (and density). Averaged from 1000 dbar to the seafloor (using 10070 profiles that extend to at least 3000 dbar, and sometimes as deep as 6000 dbar) the mean of vertical velocity variances corresponds to a sinusoidal wave amplitude of about 0.007 dbar s-1. The distribution of variances is skewed towards larger values. They also exhibit notable regional variations among and within some deep ocean basins, with generally larger variances in regions of rougher topography or stronger deep currents. Dominant vertical wavelengths estimated from Morlet wavelet transform power spectra range from 393 to 1572 dbar, most frequently 786 and 935 dbar. Vertical wavelengths are weakly anticorrelated with bathymetric roughness, expectedly since shorter wavelengths should be found near generation regions.

Satellite, reanalysis, and ocean in situ data are analyzed to evaluate regional, hemispheric and global mean trends in Earth’s energy fluxes during the first twenty years of the 21st century. Regional trends in net top-of-atmosphere (TOA) radiation from the Clouds and the Earth’s Radiant Energy System (CERES), ECMWF Reanalysis 5 (ERA5), and a model similar to ERA5 with prescribed sea surface temperature (SST) and sea ice differ markedly, particularly over the Eastern Pacific Ocean, where CERES observes large positive trends. Hemispheric and global mean net TOA flux trends for the two reanalyses are smaller than CERES, and their climatological means are half those of CERES in the southern hemisphere (SH) and more than nine times larger in the northern hemisphere (NH). The regional trend pattern of the divergence of total atmospheric energy transport (TEDIV) over ocean determined using ERA5 analyzed fields is similar to that inferred from the difference between TOA and surface fluxes from ERA5 short-term forecasts. There is also agreement in the trend pattern over ocean for surface fluxes inferred as a residual between CERES net TOA flux and ERA5 analysis TEDIV and surface fluxes obtained directly from ERA5 forecasts. Robust trends are observed over the Gulf Stream associated with enhanced surface-to-atmosphere transfer of heat. Within the ocean, larger trends in ocean heating rate are found in the NH than the SH after 2005, but the magnitude of the trend varies greatly among datasets.